The specific alterations that occur in the control of cell proliferation in chemically transformed cells is being explored in this project. Data from this laboratory, using the nontransformed AKR-2B and C3H/10T1/2 mouse embryo-derived cell lines and the chemically transformed derivatives of these cells, called AKR-MCA and C3H/MCA-58, respectively, have indicated that most of the characteristics of the transformed phenotype in these cells can be accounted for by continuous mitogenic stimulation with an endogenous growth factor. Both of the chemically transformed lines produce at least two growth factors. A radioreceptor assay for transforming growth factor, type beta (TGF beta), has been developed using TGF beta purified to homogeneity from outdated human platelets. Using this assay, one of the growth factors produced by the chemically transformed cells has been shown to be TGF beta. The AKR-MCA cells also produce small quantitites of a factor that competes for binding to the epidermal growth factor (EGF) receptor and is probably TGF alpha. Both the AKR-MCA and C3H/MCA-58 cells produce apparently larger quantities of another monolayer mitogen that does not compete in either the EGF or TGF beta radioreceptor assay. This mitogen is probably related to cellular platelet-derived growth factor (PDGF), which is a product of the c-sis gene. A PDGF radioreceptor assay is being developed to answer this question. Using the TGF beta radioreceptor assay, we have shown that both mesenchymal and epithelial cell types have receptors for this factor. However, TGF beta does not appear to be stimulatory for growth for many epithelial cell types. In fact, in collaboration with Dr. Robert W. Holley's laboratory, we have shown that TGF beta is very similar, if not identical, to the growth inhibitor purified by Doctor Holley from monkey kidney (BSC-1) cells. Both TGF beta and the inhibitor compete for binding in the radioreceptor assay, and both have similar growth stimulatory activity with mouse embryo cells in soft agar and growth inhibitory activity for epithelial cells in monolayer culture. Attempts at production of monoclonal antibodies to TGF beta have not been successful. We are now attempting production of polyclonal antibodies. (J)